A/C - Reduced cold Air - very low flow - GMC Acadia Forum: AcadiaForum.net
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post #1 of 12 (permalink) Old 08-14-2011, 11:59 AM Thread Starter
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A/C - Reduced cold Air - very low flow

This problem has occured twice since May 2011. Air Conditioning starts off "Normal", excellent flow of cold air. 1 1/2 to two hours into trip the airflow is noticed to be severly reduced and cabin getting warm. Hand on upper vents cold but hardly any airflow. Shutdown for five minutes and HVAC returns to normal with good airflow. Opened hood after shutdown, no icing evident on AC lines. Otherwise a perfect ride with no snags in almost four years. Any ideas gratefully received, not anxious to go back to a dealer as everything else is fine!

2008,SLT2,AWD,7PGR,DiaWhite,Titanium,Nav,SR,HID,<b r />HUD,Trailering prov,Convenience pkg, Cargo Pkg, and 19" Wheels.&nbsp; &nbsp; Build date 17AUG07<br />2006 Subaru Tribeca B9 AWD Base model.
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post #2 of 12 (permalink) Old 08-14-2011, 01:25 PM
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Re: A/C - Reduced cold Air - very low flow

Quote:
Originally Posted by robindcs
This problem has occured twice since May 2011. Air Conditioning starts off "Normal", excellent flow of cold air. 1 1/2 to two hours into trip the airflow is noticed to be severly reduced and cabin getting warm. Hand on upper vents cold but hardly any airflow. Shutdown for five minutes and HVAC returns to normal with good airflow. Opened hood after shutdown, no icing evident on AC lines. Otherwise a perfect ride with no snags in almost four years. Any ideas gratefully received, not anxious to go back to a dealer as everything else is fine!
Does flow increase if you lower the temp setting?

08SLT1, FWD, Summit White, Ebony leather, sunroofs, DVD, power liftgate, remote start, rear sensors
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post #3 of 12 (permalink) Old 08-14-2011, 01:44 PM Thread Starter
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Re: A/C - Reduced cold Air - very low flow

No

2008,SLT2,AWD,7PGR,DiaWhite,Titanium,Nav,SR,HID,<b r />HUD,Trailering prov,Convenience pkg, Cargo Pkg, and 19" Wheels.&nbsp; &nbsp; Build date 17AUG07<br />2006 Subaru Tribeca B9 AWD Base model.
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post #4 of 12 (permalink) Old 08-14-2011, 02:20 PM
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Re: A/C - Reduced cold Air - very low flow

Do you have a hissing noise when you turn on the AC and while it runs? If you do, that could indicate the refrigerant is leaking out. As the refrigerant level gets really low, the evaporator coil will freeze up reducing the flow of air.
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post #5 of 12 (permalink) Old 08-14-2011, 02:25 PM
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Re: A/C - Reduced cold Air - very low flow

AC evaporator boxes have a drain that allows condensed moisture to drain out the firewall/bottom of the car, it may be plugged. Check to see if water is dripping on the ground center and rear of the right front tire wheel well. The other problem could be a defective pressure cycling switch that is allowing the ac compressor to stay running too long. This will make the system operate at too low of a temperature which would cause the evaporator to ice over blocking air flow and causing the problems you are having.

2011 GMC Acadia Denali Red Jewel Cashmere interior, DVD headrests (wife and kid mover)<br />2009 GMC Sierra 1500 C/C All Terrain lots of mods daily driver<br />1987 Buick Grand National upgraded everything go fast related<br />1990 Chevy C1500 350 SS sport lowered, engine and transmission mods
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post #6 of 12 (permalink) Old 08-14-2011, 03:28 PM Thread Starter
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Re: A/C - Reduced cold Air - very low flow

No hissing noise is evident.
Condensation water draining from the forward (firewall) area........
Pressure cycling switch will be investigated.

2008,SLT2,AWD,7PGR,DiaWhite,Titanium,Nav,SR,HID,<b r />HUD,Trailering prov,Convenience pkg, Cargo Pkg, and 19" Wheels.&nbsp; &nbsp; Build date 17AUG07<br />2006 Subaru Tribeca B9 AWD Base model.
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post #7 of 12 (permalink) Old 08-14-2011, 05:26 PM
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Re: A/C - Reduced cold Air - very low flow

Manual or digital HVAC? What temp are you running the system?


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post #8 of 12 (permalink) Old 08-14-2011, 07:41 PM
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Re: A/C - Reduced cold Air - very low flow

Lambda platforms use a Thermal Expansion Valve to throttle refrigerant into the evaporator. It is possible that this unit is defective and is allowing the evaporator to be flooded with refrigerant allowing it to over cool.I was actually surprised to see the use of a TXV as opposed to a orifice tube, which is why earlier i mentioned the cycling switch. The temperature of the evaporator is dependent on system operating pressures and possibly the exit temperature of the evaporator as it passes through the TXV. TXV's typically have a bourdon tube that "reads" temperatures in the evaporator to throttle but in this system i cannot see such a tube. Either way, the icing will be independent of the set temperature on the dash as this just governs the air temp by varying the air that passes through the heater core or bypasses it.

2011 GMC Acadia Denali Red Jewel Cashmere interior, DVD headrests (wife and kid mover)<br />2009 GMC Sierra 1500 C/C All Terrain lots of mods daily driver<br />1987 Buick Grand National upgraded everything go fast related<br />1990 Chevy C1500 350 SS sport lowered, engine and transmission mods
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post #9 of 12 (permalink) Old 08-14-2011, 08:42 PM Thread Starter
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Re: A/C - Reduced cold Air - very low flow

Thank you Shadofire, I will investigate the thermal expansion valve (TXV) as well as the pressure cycling switch.

2008,SLT2,AWD,7PGR,DiaWhite,Titanium,Nav,SR,HID,<b r />HUD,Trailering prov,Convenience pkg, Cargo Pkg, and 19" Wheels.&nbsp; &nbsp; Build date 17AUG07<br />2006 Subaru Tribeca B9 AWD Base model.
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post #10 of 12 (permalink) Old 08-15-2011, 08:34 AM
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Re: A/C - Reduced cold Air - very low flow

Interesting...this happened to me a couple of weeks ago about 1.5 hours into a 2-hour drive coming home from vacation. About an hour after we returned home, I took the Acadia out to diagnose the problem, and everything was fine. I would be very interested in anything you learn.

Thanks

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